This invention relates to an apparatus for displacing high viscous substances such as lubricating grease, and the like.
Difference types of apparatus for displacing grease, also known as grease guns, are known. It is also known that by their very nature high viscous products are difficult to displace. The known apparatus generally incorporate the principles of a positive displacement pump and this requires the need to displace a high viscous product through an inlet valve arrangement, for charging the pump, which has always proved difficult.
Three basic types of grease guns are commonly known. The first type comprises a small hand type which includes a cylindrical reservoir, which is typically four to five times as long as its diameter, which is fitted with a spring loaded plunger. The stored grease is trapped between the spring loaded plunger and the head, which includes a conventional positive displacement pump. The reaction of the spring against the plunger causes an elevation in the pressure within the reservoir. As the pump is activated, a low pressure area is created in the vicinity of the inlet valve which permits the passage of grease into the pump. This low pressure area, together with the pressure created in the reservoir, is then sufficient for grease to flow through the restriction caused by the inlet valve and thereby permits the pump to be charged. The main disadvantage of this particular grease gun is that it has a relatively small reservoir capacity and a short life expectancy.
The second type of grease gun that is well known is generally known as the manually operable pail type. Here the grease is contained within a pail, typically 10 to 20 liters in capacity, which remains at atmospheric pressure. This grease gun also incorporates a displacement pump, the main feature of the pump being that the inlet valve leading into the pump can be manually opened during the inlet stroke of the pump whereby the restriction to the passage of grease into the pump is greatly reduced. A paddle arrangement is further provided which can elevate the pressure in the vicinity of the inlet port leading via the inlet valve and which can urge grease towards the inlet valve. The main disadvantages of the pail type grease gun are that they produce relatively low delivery pressures, have only a medium life expectancy and have not proved entirely reliable.
The third type of grease gun that is known is the pneumatically operable type and the main disadvantage of this type is that they are very expensive, are expensive to maintain and require a source of compressed air for their operation. Their portability is therefore greatly limited.
It is accordingly an object of the present invention to provide an improved apparatus for displacing high viscous substances and, in particular, grease.